The specific goal of this research is centered on a troublesome problem in epilepsy. There is a hard core of patients with partial epilepsy whose seizures are uncontrollable by medication and who are therefore candidates for therapeutic surgery but whose EEGs fail to lateralize the most involved hemisphere. In these patients bilateral epileptiform spiking, even from depth electrodes, makes lateralization impossible or at least uncertain. Two methods for refining the EEG data are being used and are in constant redevelopment; both depend on computer analyses to detect changes invisible to the naked eye. The first, an ictal test, is the detection of the first appearance of epileptogenic activity in a deep site and the following of extremely rapid spread of the discharge to other centers. The second is an interictal test to enhance the reaction of the tissue at different regions to benzodiazepines, it having been already shown that normal neurons develop fast frequency activity whereas lesions do not. A third line of research concerns the ultimate check-up of the EEG findings in each patient who eventually has surgery. This enables us to check the predictions of the EEG in the preoperative tests just described against the actual pathology found.